1. Statement of the Technical Field
The inventive arrangements relate to Electronic Article Surveillance (“EAS”) systems, and more particularly to EAS systems that are compliant with certain applicable safety standards.
2. Description of the Related Art
Electronic article surveillance (EAS) systems generally comprise an interrogation antenna for transmitting an electromagnetic signal into an interrogation zone, markers which respond in some known electromagnetic manner to the interrogation signal, an antenna for detecting the response of the marker, a signal analyzer for evaluating the signals produced by the detection antenna, and an alarm which indicates the presence of a marker in the interrogation zone. The alarm can then be the basis for initiating one or more appropriate responses depending upon the nature of the facility. Typically, the interrogation zone is in the vicinity of an exit from a facility such as a retail store, and the markers can be attached to articles such as items of merchandise or inventory.
One type of EAS system utilizes acousto-magnetic (AM) markers. The general operation of an AM EAS system is described in U.S. Pat. Nos. 4,510,489 and 4,510,490, the disclosure of which is herein incorporated by reference. The detection of markers in an acousto-magnetic (AM) EAS system frequently involves use of opposing pedestals placed at an exit. Each pedestal can contain an exciter coil in the form of an inductor type loop antenna comprising one or more loops of wire. A pedestal used in EAS can have a single antenna exciter coil or multiple antenna exciter coils. For example, upper and lower antenna exciter coils are sometimes used. The coils can be fed in series or in parallel by applying an EAS marker tag exciter signal. Multiple coils pedestal antenna systems are described in U.S. Pat. Nos. 8,587,489 and 5,627,516. Other types of EAS systems are known to embed the antenna in the floor in the area of an exit. These types of floor mounted coil systems are sometimes desirable for aesthetic reasons.
Markers are generally detected within a detection zone. When an exciter signal is applied to an EAS antenna in a first pedestal it will generate an electro-magnetic field of sufficient intensity so as to excite markers within the detection zone. In pedestal type systems a second pedestal will generally include an antenna having a main antenna field directed toward the detection zone (and toward the first pedestal). An exciter signal applied at the second pedestal will also generate an electromagnetic field with sufficient intensity so as to excite markers within the detection zone. When a marker tag is excited in the detection zone, it will generate an electromagnetic signal which can usually be detected by receiving the signal at the antennas.
In EAS systems that are used in European countries, it is always desirable (and many times required) that the systems have Limited Power Source (LPS) output circuits designed in accordance with International Electrotechnical Commission standard IEC/EN 60950-1 which concerns safety of information technology equipment. Output circuits designed in accordance with this standard will meet the requirements for NEC Class 2 circuits. This standard, which is established by the IEC, gives a measurement of how safe these outputs are. One of the requirements of the LPS outputs is that the peak output voltage not to exceed 42.4 Volts.